A myelodysplastic syndrome characterized by dysplasia seen in at least 10% of the early cells of 1 cell type (either red blood cells, white blood cells, or megakaryocytes) in the bone marrow. The disease is myelodysplastic syndrome with single lineage dysplasia (MONDO_0005272). Also known as: MDS with single lineage dysplasia, MDS-SLD, RA, refractory anaemia, refractory anemia.